The term mobile ad hoc network (MANET) refers to an autonomous digital communications system having multiple nodes in which all nodes may not be fully connected to all other nodes, nodes are autonomous and required to make their own routing decisions, nodes are often mobile, and standard hierarchical addressing (addresses assigned based on the sub-network the node is in) is not used. These networks don't usually use servers and routers in the traditional way and are characterized by dynamic topologies formed through the exchange of information by the nodes themselves. Individual nodes in such systems may have multiple communications interfaces but one IP address is usually used to represent all node interfaces. Typical mobile ad hoc networks include cellular telephone systems, emergency services communications systems and military battlefield communications networks.
Many MANET networks include differentiated services, which allow traffic over the network to be prioritized in accordance with different user determined “code-point” classes. Accordingly, different types of traffic may be transmitted through the network in accordance with different behaviors in order to address different quality of service (QoS) objectives and delivery requirements. Differentiated services are very important in military and emergency communications where certain types of messages must be delivered on a priority basis and certain data must be delivered on a regular schedule.
An advantaged node has features that make the node advantageous for use as a router and communications link by many other nodes in a network system. For example, advantaged nodes may have higher connectivity (perhaps by virtue of high altitude), higher bandwidth, or long haul characteristics (such as HF radio, microwave or satellite links). Advantaged nodes may also comprise nodes with interfaces to other systems that provide special services (such as internet access) or provide interfaces to additional links with significantly better connectivity and/or higher bandwidth. A good example of an advantaged node might be a military aircraft flying over a battlefield on which a large number of military ground vehicles are deployed having network nodes which are actively exchanging information with one another and with the over-flying aircraft. Unfortunately, such advantaged nodes have the potential to attract far too much network traffic causing congestion and routing bottlenecks.
A disadvantaged node has features that render it unstable or unreliable in service. Examples of disadvantaged nodes include helicopters which, by virtue of their mission, may be popping in and out of radio frequency (RF) connectivity, a node switching in and out of radio transmit silence mode (EMCON), a node low on power, or a node that is channel surfing and therefore popping in and out of the network. Disadvantaged nodes maybe of two types: either totally disadvantaged or partially disadvantaged. Partially disadvantaged nodes are usually nodes that are low on power, but they may comprise nodes affected by other disabilities: either by type or degree.
Both advantaged nodes and disadvantaged nodes can cause serious communications problems. In mobile ad hoc networks these problems can be especially acute and can arise in unpredictable ways as mobile nodes move and their network links change. In the past, solutions to this problem have been discussed involving the use of modified route discovery routing algorithms adapted for load balancing and for selecting better routing pathways' as opposed to the shortest pathway. Unfortunately, such solutions are usually difficult to implement, involve a considerable increase in computational overhead, and are likely to be most useful in link state type network routing systems.